Various therapeutic and diagnostic procedures require that a substance be infused into a prescribed region of a patient, such as into a target deep brain location in the patient's brain, using a delivery cannula. It may be important or critical that the substance be delivered with high accuracy to the target region in the patient and without undue trauma to the patient. MRI-guided deliveries typically employ long lengths of tubing resulting in relatively large “dead spaces” that often result in a volume of medical substance that may be wasted or unused. Because of the high cost of such medical substances, it may be desirable to reduce the amount of substance that is wasted or unused.